There has been a tendency to use direct reduced iron or small lumps of pig iron for producing qualified steel products. In a conventional electric furnace, several methods have been used to charge raw materials into the furnace. One of them is to batch-charge raw materials together with steel scrap into the furnace by use of a bucket or to consequently charge them from hopper to the charging hole of the furnace roof through weigh conveyor. However, it has a disadvantage that the waste heat generated from the furnace is not utilized efficiently due to the direct exhaust into the atmosphere through the conventional bag house instead of being used to preheat raw materials, and therefore it does not contribute to efficient energy utilization and cost reduction.
Heretofore, it has been desired to improve the virginity of steel products by diluting various impurities of the steel scrap through direct reduced iron or small lumps of pig iron so as to remove undesirable effects on steel products caused by the impurities, continuously charge raw materials into furnace so as to reduce time consumption occured by batch charging with bucket and eliminate boiling phenomena which occur at the time when charging direct reduced iron together with steel scrap through a bucket, and use the same duct which permits flowing the waste gas generated from the steel making furnace as well as charging the direct reduced iron into the furnace.